Large-sizing and high definition of the screen for various displays such as a liquid crystal display, a plasma display and so forth have been advanced, and the visibility and handling to be improved are demanded. In order to improve these, optical films exhibiting various optical functions are proposed. Specific examples of the optical film include an anti-reflection film, an anti-glare film, a hard coat film, an anti-stain film, an anti-static film a view-angle improving film, a phase difference film, a polarizing plate protective film, an optical compensating film, a luminance enhancing film, and a light diffusion film. These films tend to be desired to have at least two kinds of functions at the same time.
On the other hand, large-sizing of various displays such as a flat panel display, and so forth, accompanied simultaneously with demand of manufacturing cost reduction has also been advanced. Though a highly advanced technique is desired to produce the above optical films, more uniform quality besides this is demanded than before in order to correspond to large-sizing of the displays.
The aforementioned optical film is manufactured by casting and drying of the resin dissolved in the solvent and molten resin. Many processes such as casting, orientation, coating, drying, surface treatment, heat treatment and winding processes are required to manufacture the aforementioned optical film. It has been required to remove such contaminants as the dust and resin film fragments deposited on the film in these processes.
To remove the contaminants on the optical film, proposals have been submitted to disclose a means for removing the contaminants, such as an adhesion type web cleaner (e.g. Patent Documents 1 and 2), brush type cleaner (e.g. Patent Document 3) and air type web cleaner (e.g. Patent Document 4), in addition to the methods of performing the entire manufacturing processes in a clean room.
[Patent Document 1] Japanese Patent O.P.I. Publication No. 2002-334429
[Patent Document 2] Japanese Patent O.P.I. Publication No. 2004-189967
[Patent Document 3] Japanese Patent O.P.I. Publication No. 10-309541
[Patent Document 4] Japanese Patent O.P.I. Publication No. 7-68226